Jet turbine reliability

Very informative - thanks!

Please keep us posted on your progress in testing and best of luck.

On 6/5/2015 11:04 PM, wrote:
I've been working on the jet glider concept for over 10 years. 5 years ago, after a false start with somebody who never delivered what was promised I bought a couple of AMT Titan engines and have almost finished fitting them to my Ventus C 17.6 A fuselage. They are fully retractable. Just some electrical connectors to go and we're ready to do engine runs.
Yes if one engine makes a turbo, two make a self launch and two are better than one even if the installation is a little more difficult. As a slight bonus two Titans of 400N each are in fact cheaper than one Nike of 800N thrust from the same manufacturer.

Fuel consumption: Should get to 2000 feet above ground for around 5 to 6 litres of jet A/jet oil 4.5% mix. Compares favorably with aerotow. Retrieves cheaper than by car, without the outlanding risk and way cheaper than aerotow retrieves. I made a jet performance spreadsheet for takeoff and climb performance. Seems to validate against flying jet gliders. Predicted climb without water ballast nearly 800fpm (SL, standard day at 70% thrust on both engines. Will still climb 280fpm on one and 400fpm on one at 85%. Retrieve range close to 250km. I got 45 litres of fuel and the engines into the A model fuselage without impinging on any space used by pilot or equipment.

Noise: Enough installed thrust and good rate of climb means you're away from the ground quickly. Use airframe shielding and aviation industry noise reduction methods. Existing jet gliders do none of this. I saw and heard Bob Carlton's Super Salto at Avalon in 2009. It wasn't very noisy at all. Neither, I am told, was the Jet Silent he flew a couple of years earlier. I've got a couple of translating ejector nozzles just like the early DC-8 although in this case they are translating in order to minimise engine length for retraction.
Don't forget the noise stops at top of launch, unlike that from a towplane.

Safety: There are two things that can go wrong with the jets. They could catch fire or have a RUD event. I have a fire detection system and Halon fire extinguisher system for the former and 4130 steel around the compressor and turbine sections and the engine compartment is lined with fiberfrax over 8 layers of 170 gram kevlar. The Titan turbine blades are almost the same mass and speed as a .22LR rifle bullet so I took out the .22 and made some samples and tested.
A few years ago a bad batch of compressors made it into model airplane jet world. I gather when they failed some bits dribbled out the front of the engines. I'm not too worried about this.

Operations: Two engines means that launch failures should be rare. You only need to get one out of two running to fly away from a potential outlanding and extending the engines is not a large drag increment. The engines will NEVER be run at 100%. 70% is enough to meet CS22 takeoff at 410Kg and at 500Kg 85%.
Best retrieve range is by running both engines. Should get to 17000 feet above engine start point after a 2000 foot launch.

As for a few other points raised he The engine in the 304 jet appears to be a Titan with external shielding and I'm told the M&D engine internals are bought from AMT and are the Titan. The Titan seems to be rapidly becoming the standard 400N thrust engine.Certainly seems to be from what I saw. No external shielding which may be why the difficult and expensive EASA certification process just like Draline with the AMT Olympus(8 years.Different starter and case and I'm told, combustor section.
Certification will be the death of this sport.It will make anything vastly more expensive, particularly in a low volume business like soaring.

Anyway, I'm looking forward to having this flying over the next few months and the test flying program should be a lot of fun.

I'm also looking forward to hearing about the flights of the GloW. Should be a fun glider and the electric wheel is a fine idea.

I'll also be testing the new total energy system which completely rejects horizontal gusts and two other new ideas which may change the way glider variometer systems are done.

Mike Borgelt
Borgelt Instruments

--
Dan Marotta

On Friday, June 5, 2015 at 3:15:06 AM UTC-7, Craig Lowrie wrote:
The HPH Shark takes 28 liters of Jet A1 + 4% Aeroshell 500. That will
give about 55 minutes cruising at 80-90 knots... The technique is not
climb and glide, rather dolphin flying... pulling up in any residual
energy and in notime you have gained quite a lot of height... It works.
Typically The Shark Jet will do 170km on a tank. The FES version will do
about 100km, whilst the Shark MS (Self Launcher) will do over 300km
on a tank...

Craig

At 08:30 05 June 2015, wrote:
"Gobble as well as gulp...with Jet A at +/- $5 a gallon and AeroShell
560
at $15 a quart that works out to north of $100 to fill up the JS-1"

Well......you could certainly calculate a worst case scenario like that.
But as 11USG of Diesel / 2-stroke (4%) oil mix is flight manual
approved,
this may be a more commonly employed option.

(US prices: 10.6USG @ $2.70 + 0.42USG & $20) is $37.

Glider pilots: Tighter than a fish's a....... :P


For reference, an ASH26E uses about 2 liters for a warm up and climb to 2500 ft agl, and will do 680 Km on its 16 liter tank (according to the book - never had a retrieve that long!). To do that you climb to altitude limits then fold the engine and glide, and repeat as needed. Is the climb performance on a jet significantly better so that the climb and glide technique improves retrieve range over a level cruise?

Climb and glide with the Jet is NOT optimal...

The best speed for the Jet engine is probably over 200 knots (!)....
and whilst this is not possible, the faster the better... so after
briefly climbing away from a field, it is better to accelerate to 80-90
knots and then dolphin-fly, varying speed in accordance with any
residual lift (these is always some)... This technique will produce
the best range...

Craig

At 19:02 06 June 2015, jfitch wrote:
On Friday, June 5, 2015 at 3:15:06 AM UTC-7, Craig Lowrie
wrote:
The HPH Shark takes 28 liters of Jet A1 + 4% Aeroshell 500.
That will=20
give about 55 minutes cruising at 80-90 knots... The technique
is not=20
climb and glide, rather dolphin flying... pulling up in any
residual=20
energy and in notime you have gained quite a lot of height... It
works. =
=20
Typically The Shark Jet will do 170km on a tank. The FES
version will do=
=20
about 100km, whilst the Shark MS (Self Launcher) will do over
300km=20
on a tank...
=20
Craig
=20
At 08:30 05 June 2015, wrote:
"Gobble as well as gulp...with Jet A at +/- $5 a gallon and
AeroShell=20
560
at $15 a quart that works out to north of $100 to fill up the
JS-1"

Well......you could certainly calculate a worst case scenario
like
that.=
=20
But as 11USG of Diesel / 2-stroke (4%) oil mix is flight
manual=20
approved,
this may be a more commonly employed option.=20

(US prices: 10.6USG @ $2.70 + 0.42USG & $20) is $37. =20

Glider pilots: Tighter than a fish's a....... :P


For reference, an ASH26E uses about 2 liters for a warm up and
climb to
250=
0 ft agl, and will do 680 Km on its 16 liter tank (according to the
book -
=
never had a retrieve that long!). To do that you climb to altitude
limits
t=
hen fold the engine and glide, and repeat as needed. Is the climb
performan=
ce on a jet significantly better so that the climb and glide
technique
impr=
oves retrieve range over a level cruise?

Op zaterdag 6 juni 2015 21:02:52 UTC+2 schreef jfitch:
For reference, an ASH26E uses about 2 liters for a warm up and climb to 2500 ft agl, and will do 680 Km on its 16 liter tank (according to the book - never had a retrieve that long!). To do that you climb to altitude limits then fold the engine and glide, and repeat as needed. Is the climb performance on a jet significantly better so that the climb and glide technique improves retrieve range over a level cruise?

Yes. The higher the thrust/weight ratio is, the more it pays off. Best CLIMB speed for example for a 450 kg ship and a 800N jet is way above 100 kts.

For highter thrust/weight ratio's, fuel efficiency goes up too; a dolphining flight can get similar mileage to a decent car, even with the typical fuel burn of such a jet (70 kg/hr for the 800N AMT).

I have seen various slightly different graphs from JS for ways of using their jet but consistently they predict the greatest theoretical range being from a full power climb at around 80 knots and then glide.

Next best is the economical cruise at about 75,000 rpm and around 75-80 knots - similar to the HpH scenario but JS haven't included the dolphining effect. All flight traces I have found of the JS1 jet being used for real life retrieves seem to show it being used for slow climb and cruise around 75 knots.

I am not sure if including extra range from dolphining gives a valid comparison as there is no stated model of the amount of dolphin-worthy lift being flown through. Also I would have thought that if there was enough lift to gain significant range from dolphining I would turn off the jet and get proper netto and STF info to dolphin efficiently - bearing in mind that these computations rely on the polar in the computer being the same as the glider which it clearly isn't with any engine running (even without considering prop/jetwash effects on the fin probe).

What range does JS predict when using these techniques?


On Sunday, June 7, 2015 at 3:12:48 AM UTC-7, wrote:

I have seen various slightly different graphs from JS for ways of using their jet but consistently they predict the greatest theoretical range being from a full power climb at around 80 knots and then glide.

Next best is the economical cruise at about 75,000 rpm and around 75-80 knots - similar to the HpH scenario but JS haven't included the dolphining effect. All flight traces I have found of the JS1 jet being used for real life retrieves seem to show it being used for slow climb and cruise around 75 knots.

Some comments from actual experience:
I have flown both self launching and sustainer gliders (Schemmp & AS), and now own a JS with turbine. I have no experience with the FES, although I have seen it ground run. For this post I will mostly ignore the FES, although I think it is an excellent system, save for the minimal drag which is a large concern for contest pilots. Plus, our national electicity supplier are all out of electricity and options, so charging might be difficult at times 😄 ( just kidding)

Operation:
The jet is by far the easiest to deploy, start, run, shut down and retract. It is a simple 3 step process. Turn on the master switch, switch the turbine to run, wait for turbine to spool up, and add power by turning a knob, all on one 57mm LCD instrument. The software can actually spool up the turbine to max rpm automatically, elliminating step 3. Shutting down is equally effortless. Switch off, and the controller does the rest. It waits for the turbine to cool, and then retracts automatically. Once retracted, you can turn the engine master switch off.
Safety: I have deployed the jet sucessfully from 150' agl (thats feet agl). Normally, I switch the master on at about 1000' agl. I extract the engine at 600', but do not start it yet. At 250' agl I switch on the jet, and it is at idle rpm at 150-160' agl.
Compared to the AS wankel engine, which I would start that at 600'. The solo sustainer I would normally start at 1000' agl. Both the wankel and turbo engines have a significantly higher workload than the jet.
In all of these scenarios I obviously have a landing field available in case of a failed start. I have had failed starts, and subsequent outlandings, with all three systems. No system is 100% reliable.
Initially (I had one of the early installations ) the reliability was about 60%. M&D and JS have however ironed out the initial problems and reliability issues (expected with any new system). I dont keep exact track, but I have not had a failed start or problem for the last year, except a glowplug glitch on the ground before flight for the last 18 months, so reliabilty is now a small worry.
Use
I have used the jet 5 times now in the last 100 cross country flights, with the longest retrieve about 220km straight line through dead air, I climbed from about 1000' agl in light rain, flying at about 70kts ias. I continued climbing up to about 11000' amsl, or 6000' agl and switched off the jet. I burned 30 liters of fuel. I estimate that a 380-400km range is possible in dead air. The rain stopped after the first 5km.
General:
Maintenance is all but non existant, apart from the ocasional wipe off to get rid of dust, and a visual pre flight inspection. I had the actuator that extends the engine replaced (under guarantee). Refueling is very easy. I prefer using Jet A1, as I think it is a more efficient fuel, and it smells better 😄. The fuel filter gets cleaned or replaced during the annual inspection.
Noise in the cockpit is not intrusive, even when wearing no earplugs or a headset. The radio can be heard clearly through the normal speakers, as can the vario. Noise on the ground during a flypast is less than the traditional internal combustion engine. It gets noisy when doing a stationary ground runs, but no more than a prop driven self launcher.
When the jet has not been in use for an extended period, a ground start before flight is advisable to purge the fuel supply of air, ensuring an immediate start in the air.
As the glow plug and fuel pump needs constant current during operation, it is advisable to have your battery charged up.
The jet goes from master on to full power in 45 seconds. Idle rpm is 30 000 rpm, and full power delivers just under 100k rpm. I normally limit the rpm to 95k. At 95k rpm the fuel burn is 40liters per hour, and fuel capacity is 42 liters. Fuel burn drops to about 35 liters per hour at 9000' amsl. Exhaust gas temprerature is about 650 deg celcius at full power. Temperature change on the vertical tail skin is minimal, even on the ground as the engine is slightly offset.
On the test aircraft, during the endurance test, which was flown for an hour above 20 000' amsl and at 110 000 rpm continously, a blade did separate from the rotor. The blade was contained in the housing with no other damage to the engine or glider. This specific engine had run all the certification tests before throwing the blade. I dont know how many hours it had, but it was significant.
I can honesly say this is the best system if you want to avoid landouts. The airfield I fly from mostly has a tug available, so I dont need a self launcher. Apart from the simplicity and efficiency of the jet, the biggest factor is the sheer joy of playing around with the jet running.

OG--thanks for your input.

What is Standard Operating Procedure regarding leaving jet fuel in tanks between flight? Should you always leave the tanks full or do you pump all the fuel out after flight and refill before next possible use?

Once you buy Jet A, how long would you keep the fuel before you would consider it "bad"?

What is Jonkers/M&D warranty regarding jet and ECU?

I leave the fuel in the tank, but replace it every 3 months, should it not be used in that period. I am not sure what Jet A1 specs say about shelf life, but I think this is about right.
Seeing as the jet is still in evaluation/developmental phase, I am not actually sure what the warranty is. That being said JS/M&D stands behind the product. My actuator was replaced at no cost. Barring obvious misuse/abuse I am sure they will be more than reasonable with any latent defect. But I dont speak for either of them, so dont quote me😉

On Sunday, June 7, 2015 at 9:28:54 PM UTC+1, OG wrote:
I leave the fuel in the tank, but replace it every 3 months, should it not be used in that period. I am not sure what Jet A1 specs say about shelf life, but I think this is about right.
Seeing as the jet is still in evaluation/developmental phase, I am not actually sure what the warranty is. That being said JS/M&D stands behind the product. My actuator was replaced at no cost. Barring obvious misuse/abuse I am sure they will be more than reasonable with any latent defect. But I don't speak for either of them, so dont quote me😉

There is a 2012 UK General Aviation Safety Information Leaflet that advises a "shelf life" of 3 months for Avgas and 6 months for Jet A1. It advises keeping tanks 90% full to reduce deterioration or water contamination.